Category: Cosmology

Little Strings And Big Ones

On By rolcottIn Cosmology, Physics: Quantum Mechanics, Physics: Waves, UncategorizedLeave a comment

It’ll be another hot day so I’m walking the park early. No geese in the lake — they’ve either flown north or else they’re attacking a farmer’s alfalfa field. A familiar voice shatters the quiet. “Wait up, Moire, I got questions.”

“Good morning, Mr Feder. First question, but please pick up your pace, I want to get back to the air conditioning.”

“I thought string theory was about little teeny stuff but this guy said about cosmic strings. How can they be teeny and cosmic?”

“They can’t. Totally different things, probably. Next question.”

“C’mon, Moire, that wasn’t even an answer, just opened up a bunch more questions.”

“It’s a tangled path but the track mostly started in the late 18th Century. Joseph Fourier derived the equation for how heat progresses along a uniform metal bar. Turned out the equation’s general solution was the sum of an infinite series of sine waves.”

“Sign waves? Like a protest rally?”

“Haha. No, s‑i‑n‑e, a mathematical function where something regularly and smoothly deviates about some central value. Anyhow, mathematicians soon realized that Fourier’s cute trick for his heat equation could be applied to equations for everything from sound waves to signal processing to pretty much all of Physics. Economics, even. Any time you use the word ‘frequency‘ you owe something to Fourier.”

“If he ain’t got it in writing from the Patent Office, I ain’t paying nothing.”

“It’s not the kind of thing you can patent, and besides, he lived in France and died almost two centuries ago. Be generous with your gratitude, at least. Let’s move on. Fourier’s Big Idea was already <ahem> in the air early in the 20th Century when Bohr and the Physics gang were looking at atoms. No surprise, they extended the notion to describe how electronic charge worked in there.”

“I’m waiting for the strings.”

“The key is that an atom’s a confined system like a guitar string that only vibrates between the bridge and whatever fret you’re pressing on. Sound waves traveling in open space can have any wavelength, but if you pluck a confined guitar string the only wavelengths you can excite are whole number multiples of its active length. No funny fractions like π/73 of the length no matter how hard or soft you pluck the string. Atoms work the same way — charge is confined around the nucleus so only certain wave sizes and shapes are allowed.”

“You said ‘strings.’ We getting somewhere finally?”

“Closing in on it. String theory strings aren’t just teeny. If your body were suddenly made as large as the Observable Universe, string theory is about what might happen inside a box a billion times smaller than your size now.”

“Really tight quarters, got it, so only certain vibrations are allowed.”

“Mm-hm, except it’s not really vibration, it would be something that acts mathematically like vibration. Go back to your guitar string. Plucking gives it up‑down motion, strumming moves it side‑to‑side. Two degrees of freedom. The math says whatever’s going on in a string theory box needs 8 or 11 or maybe 25 degrees of freedom, depending on the theory. At the box‑size scale if there’s structure at all it looks nothing like a string.”

“Then how about the big cosmic strings? What’s confining them?”

“Nothing, and I mean that literally. If they exist they’re bounded by different flavors of empty space. It goes back to what we think happened right after the Big Bang during rapid space expansion. Whatever forces drove the process were probably limited by lightspeed. Local acceleration in one region wouldn’t immediately affect events in regions lightyears away. Nearly adjacent parts of the Universe could have been evolving at very different rates. Have you ever watched the whirlpools that form when a fast‑moving stream of water meets a slower‑moving one?”

“Fort Lee had a storm‑sewer pipe that let into the Hudson River. You got crazy whirlpools there after a hard rain.”

“Whirlpools are one kind of topological defect. They die away in water because friction dissipates the angular momentum. Hiding behind a whole stack of ifs and maybes, some theorists think collisions between differently‑evolving spacetime structures might generate long‑lived defects like cosmic strings or sheets.”

~~ Rich Olcott

Not A Hum, A Rumble

On By rolcottIn Cosmology, Gravitational astronomy, UncategorizedLeave a comment

Vinnie taps on the magazine. “Sy, you’ve done it again. We ask you one question, you spend a lot of time talking about something else entire. They got this article here” <tap> “says the NANOGrav team captured the hum of the Universe. Al and me, we ask you about that and you get us discussing pulsars. Seems to me,” <tap tap> “that if you got a pulsar and the pulses got only a 3% duty cycle they’d sound more like clicks and,” <taptaptaptap> “if it’s a 10 millisecond pulsar that’s a hundred per second and they’d be more like a low‑pitched buzz, nothing like a hum.”

“One more short detour, Vinnie, sorry. Remember when we discussed the VLA, the Very Large Array of radio telescopes in northern New Mexico?”

“Sorta. I do remember visiting the place, out in the desert miles away from anywhere. They’ve got a couple dozen dish antennas each as wide as a four‑lane road, all spread out along railroad tracks. Big dishes for catching weak signals I understand, but I forget why there’s lots of dishes instead of one huge one or how that even works.”

“One reason is simple mechanics. A huge dish would try to sail away in the desert wind. VLA admins even have to safe‑mount those 25‑meter ones when things get gusty. But the real reason goes to how the array works as one big instrument. Here’s a hint — the dishes can be miles apart and lightspeed isn’t infinite.”

“Ah, that joggled my memory. It’s about when a signal comes in from some nova or something, each dish registers it with a slightly different arrival time and then the computers play match‑up games with all the time differences to figure exactly what angle the signal came from, right?”

“Roughly. The VLA’s multi‑dish design is about being able to resolve signal sources that are close together in the sky so yeah, slightly different angles. The Event Horizon Telescope team used the same strategy and a collection of radio dishes all over the world to produce those orange‑ring images of supermassive black holes. NANOGrav and the other Pulsar Timing Arrays sort of the flip the strategy.”

“At last we get to NANOGrav. Wait, they use lots of antennas to send signals to a star?”

“Nothing like that, Al. No, they use just a few antennas but they track the timing of many pulsars. About 70 at last count.”

“But we know what the timing is, to nanoseconds you said.”

“One word, Vinnie. ‘Frames‘.”

“Aw geez, Sy. Again?”

“Mm-hm. In the pulsar’s frame, it’s majestically rotating at a steady pace, tens or hundreds of times per second relative to its neighbors. Its beam proudly announces its presence on an absolutely regular schedule save for a small but steady slow‑down. In our frame, though, things can happen to a pulse as it heads our way.”

“Like what?”

“It might pass through a molecular cloud. We know those exist. Photons in the right wavelength ranges could interact with cloud components. That’d delay them, stretch the pulse, might even create interference between successive pulses. On the theory side, some cosmologists think the Universe may hold objects like cosmic strings or curvature‑induced domain walls that could delay, deflect or otherwise mess up a pulse. The best possibility, though, is that a gravitational wave could cross the path of a pulse en route to us.”

“Why is that a good thing?”

“Because they’d interact to alter that pulse’s timing. Gravitational waves stretch and squeeze time as they squeeze and stretch space. If a wave crosses a traveling pulse, the pulse will get here either early or late depending. Better yet, if we track enough pulsars scattered across the sky we might even see a parade of offset timings as the wave encounters different pulse beams. Hasn’t happened yet, though. The NANOGrav reports so far are about the background variation as waves from everywhere traverse the paths we’re watching.”

“The article says a hum.”

“Hum sounds come in waves per second. The gravitational background happens in waves per decade, such a low frequency even elephants couldn’t hear it.”

“OK, it’s rumble, not a hum. But why either one?”

~~ Rich Olcott

Symmetry And The Loopholes

On By rolcottIn Cosmology, Mathematics, UncategorizedLeave a comment

“So, we’ve got geometry symmetry and relativity symmetry. Is that it, Sy?”

“Hardly, Al. There’s scores of them. Mathematics has a whole branch devoted to sorting and classifying the operations and how they group together. Shall I list a few dozen?”

“Ah, no, don’t bother, thanks. You got one I’d recognize?”

“How about charge symmetry? Flip an electron’s negative charge and you’ve got a positron that has exactly the same mass and the same interaction with light waves. OK, positrons move opposite to electrons in a magnetic field which is how their existence was confirmed, but charge is s a fundamental symmetry for normal matter.”

“Oh, right, charge is a piece of that CPT symmetry you hung your anti‑Universe story on. Which reminds me, you never said what the ‘P’ stands for.”

“Parity, as in Charge‑Parity‑Time. Before you ask, ‘parity‘ is left-right symmetry. Parity symmetry says you can replace ‘clockwise‘ with ‘counterclockwise‘ in a system and the equations describing the system will give perfectly good predictions. Time symmetry is about time running forward or backward. The equations are happy either way. The CPT theorem says the three symmetries are solidly tied together — you can’t flip one without the other two tagging along. If some process emits particle X with clockwise spin, there’s some equivalent process that soaks up an anti-X if it’s spinning counterclockwise. Very firm theorem, lots of laboratory evidence for it from electromagnetism and the nuclear strong force. But.”

“But?”

“But Chien‑Shiung Wu did an experiment that showed the nuclear weak force doesn’t always obey CPT rules. Her worked proved we live in a handed Universe. She should have gotten a Nobel for that, but it was last century and the Nobel Committee was men‑only. Two theory guys copped the prize that should have gone to the three of them. The theory guys protested but the Committee ignored Wu anyway. Sometimes things aren’t fair.”

“Tell me about it. So the theory’s got a loophole?”

“Apparently, but to my knowledge no‐one’s found it. Some string theories claim to hint at an explanation but that’s not much help, considering.”

“Huh. Could the loophole maybe be an example of symmetry breaking?”

“Very good question. I think it’s a qualified probably but that’s a guess.”

“Sy, I think that’s the wishy-washiest you’ve ever been.”

“One of my rules is, when you’re going out on a limb be sure you’re properly roped to the tree. In this case I’m generalizing from a single sample.”

“You’re gonna tell me, right?”

   Professor Higgs presents
       the Higgs Bozo.

“Just the bare outline because I don’t want to get into the deep weeds. Back in the 1960s Physics was in trouble because the nuclear strong force particles that bind the nucleus together were found to have mass and move slowly. Strong‑force theory at the time said they should be massless and move at lightspeed. The theory depended on part of the potential energy varying with the symmetry of a circle. Then Higgs—”

“The Higgs Boson guy?”

“That’s him. Anyway, he published a three‑page paper showing that those binding particles aren’t controlled solely by the nuclear strong force. Because they have a charge they also engage with the electromagnetic field. Electromagnetism is a lot weaker than the strong force, but it’s strong enough to deform the theory’s circle into an ellipse. Breaking the circular symmetry in effect gives the particles mass and slows them down.”

“So where’s the boson come in? I thought it’s what makes mass for everything.”

“Absolutely not, probably. The protons and neutrons have plenty of mass on their own, thank you very much. It’s only those strong-force particles that gain mass, less than 1% of the nucleus total. But the whole story is a great example of how making a system less symmetrical, even a little bit, can completely change how it operates. We think that’s what drove the Big Bang’s story. The early Universe was so dense and hot it was a perfectly symmetrical quark soup — chaos all the way down. Space expansion opened successive symmetry loopholes that permitted layers of structure formation.”

<looking at hands> “I don’t feel unsymmetrical.”

“Trust me, deep down you are.”

~~ Rich Olcott

Reflection, Rotation And Spacetime

On By rolcottIn Cosmology, Mathematics, Physics: Einstein, UncategorizedLeave a comment

“Afternoon, Al.”

“Hiya, Sy. Hey, which of these two scones d’ya like better?”

“”Mm … this oniony one, sorta. The other is too vegetable for me ‑ grass, I think, and maybe asparagus? What’s going on?”

“Experimenting, Sy, experimenting. I’m going for ‘Taste of Spring.’ The first one was spring onion, the second was fiddlehead ferns. I picked ’em myself.”

“Very seasonal, but I’m afraid neither goes well with coffee. I’ll take a caramel scone, please, plus a mug of my usual mud.”

“Aw, Sy, caramel’s a winter flavor. Here you go. Say, while you’re here, maybe you could clear up something for me?”

“I can try. What’s the something?”

“After your multiverse series I got out my astronomy magazines to read up on the Big Bang. Several of the articles said that we’ve gone through several … um, I think they said ‘epochs‘ … separated by episodes of symmetry breaking. What’s that all about?”

“It’s about a central notion in modern Physics. Name me some kinds of symmetry.”

“Mmm, there’s left‑right, of course, and the turning kind like a snowflake has. Come to think — I like listening to Bach and Vivaldi when I’m planet‑watching. I don’t know why but their stuff reminds me of geometry and feels like symmetry.”

“Would it help to know that the word comes from the Greek for ‘same measure‘? Symmetry is about transformations, like your mirror and rotation operations, that affect a system but don’t significantly change to its measurable properties. Rotate that snowflake 60° and it looks exactly the same. Both the geometric symmetries you named are two‑dimensional but the principle applies all over the place. Bach and the whole Baroque era were just saturated with symmetry. His music was so regular it even looked good on the page. Even buildings and artworks back then were planned to look balanced, as much mass and structure on the left as on the right.”

“I don’t read music, just listen to it. Why does Bach sound symmetric?”

“There’s another kind of symmetry, called a ‘translation‘ don’t ask why, where the transformation moves something along a line within some larger structure. That paper napkin dispenser, for instance. It’s got a stack of napkins that all look alike. I pull one off, napkins move up one unit but the stack doesn’t look any different.”

“Except I gotta refill it when it runs low, but I get your drift. You’re saying Bach takes a phrase and repeats it over and over and that sounds like translational symmetry along the music’s timeline.”

“Yup, maybe up or down a few tones, maybe a different register or instrument. The repeats are the thing. Play his Third Brandenberg Concerto next time you’re at your telescope, you’ll see what I mean.”

“Symmetry’s not just math then.”

“Like I said, it’s everywhere. You’ve seen diagrams of DNA’s spiral staircase. It combines translation with rotation symmetry, does about 10 translation steps per turn, over and over. The Universe has a symmetry you don’t see at all. No‑one did until Lorentz and Poincaré revised Heaviside’s version of Maxwell’s electromagnetism equations for Minkowski space. Einstein, Hilbert and Grossman used that work to give us and the Universe a new symmetry.”

“Einstein didn’t do the math?”

“The crew I just named were world‑class in math, he wasn’t. Einstein’s strengths were his physical intuition and his ability to pick problems his math buddies would find interesting. Look, Newton’s Universe depends on absolute space and time. The distance between two objects at a given time is always the same, no matter who’s measuring it or how fast anyone is moving. All observers measure the same duration between two incidents regardless. Follow me?”

“Makes sense. That’s how things work hereabouts, anyway.”

“That’s how they work everywhere until you get to high speeds or high gravity. Lorentz proved that the distances and durations you measure depend on your velocity relative to what you’re measuring. Extreme cases lead to inconsistent numbers. Newton’s absolute space and time are pliable. To Einstein such instability was an abomination. Physics needs a firm foundation, a symmetry between all observers to support consistent measurements throughout the Universe. Einstein’s Relativity Theory rescued Physics with symmetrical mathematical transformations that enforce consistency.”

~~ Rich Olcott

Time And The Egg

On By rolcottIn Cosmology, UncategorizedLeave a comment

I unlock my office door and there’s Vinnie in the client chair flipping a coin from hand to hand. If my building ever switches to digital locks he’d take it as a challenge. “Morning, Vinnie.”

“Morning, Sy. Been reading your multiverse series and something you said bothered me.”

“What’s that?”

“Back when you wrote up your anti-Universe idea that some other group had come up with first—”

“Don’t remind me.”

“—you mentioned how time going backwards makes for negative energy, like that’s obvious. It ain’t obvious to me.”

“Okay … Ah. What word keeps coming up in our black hole discussions?”

“Geez, frames again? Universes ain’t black holes.”

“Don’t be so sure. Suppose there’s a black hole Event Horizon that encloses our entire Observable Universe. An Event Horizon’s diameter depends on how much mass it has inside. Astronomy’s given us an estimate of how much normal matter our Observable Universe contains. I adjusted that number upward to account for the expected quantity of dark matter plus dark energy’s equivalent mass. When I plugged that grand total into Schwarzchild’s formula for the diameter of an Event Horizon, the result was about seven times wider than what we can observe. We could be inside a huge black hole but we’ll never know either way.”

“Whoa! Wouldn’t we notice a drift towards the singularity at its middle?”

“Not if we’re reasonably far out or if the drift rate is tiny compared to the slow chaos of intergalactic space. Mind you, it took us centuries to develop the technology that told us we’re inside the Milky Way and two‑thirds of the way out from the core.”

“We used frames for thinking about going really fast or being outside a black hole. Now we’re inside one or maybe not. How’s frames gonna help us with that?”

“Well, not the inertial frames where we compared relativistic observers, but the idea is similar. A traveler in an intense gravity field experiences slower time in its inertial frame than a distant partner does in theirs. Clocks appear to run weirdly if they’re compared between separate frames whose relative velocities are near lightspeed.”

“Yeah, that’s what we said.”

“Now picture two observational frames, one here in our Universe and one in the anti‑Universe if there is one. Time in the two frames flows in opposite directions away from the Big Bang between them. The two‑frames notion is a convenient way to think about consequences. Negative energy is one.”

“Now we’re getting somewhere. So give.”

“Well, what does energy do?”

“It makes things happen.”

“Negative energy does, too, considered from inside its frame. Looking from our frame, though, negative energy makes things unhappen. This spoon on our table has gravitational potential energy relative to the floor, right?”

“Yeah, you push it over the edge it’ll fall down.”

“But looking from our frame at a similar situation in the anti‑Universe running on anti‑time, an anti‑spoon on its floor has negative gravitational potential energy. We’d see it fall up to its table. Make sense?”

“Gimme a minute.” <pause> “Kinda hard to visualize but I’m starting to get there.” <longer pause> “Alright, you know I hate equations but even I know about Einstein’s E=mc². That c² is a square so it’s always positive so if E is negative then the mass gotta be negative, too.”

“From our frame all mass in the anti‑Universe looks negative. Negative mass would attract negative mass just like positive mass attracts positive mass here. Gravity in the anti‑Universe would work exactly the same way as our gravity does, so where’s the problem?”

“Gimme another minute.” <more pausing> “Suppose that spoon was an anti‑egg. You’re sayin’ when it goes splat over there, we’re gonna see it unsplat? Unsplatting uses up entropy. How about the ‘Entropy always increases‘ rule?”

“Right on the unsplat, wrong on the other. The full statement of Thermodynamics’ Second Law says that entropy never decreases in an isolated system. You can’t get much more isolated than being a separate Universe — no inputs of energy or matter from our Universe or anywhere else, right? From our frame, it looks like the anti‑Universe flipped the Second Law but that’s only because we’re using the wrong clock.”

~~ Rich Olcott

A Matter of Degree

On By rolcottIn CosmologyLeave a comment

“Wait, Sy, you said something about my matryoshka‑cascade multiverse, that the speed of light might not match between mama and baby Universes. How can that be?”

“Deep question, Susan. The answer is that we don’t know. Maybe gravitational stress at a supermassive black hole’s singularity is intense enough to birth a new Universe inside the Event Horizon, or maybe not. Suppose it does. We don’t have theories strong enough to determine whether the speed of light inside there would or would not match the one we have out here.”

“Talk about pregnant questions.” <sips latte> “Ah! Here’s another thing. Both my matryoshki and your bubbly multiverse are about spreading Universes across space. Neither one addresses the timeline splits we started talking about. Maybe I decide on noodles for lunch and another me in a different Universe opts for a sandwich, but how about one me that splits to follow parallel paths right here? Could a multiverse work that way?”

“Another deep question. Timeline splits require a five‑dimensional spacetime. Want to talk about that?”

“Just a moment. Oh, Al, can I have another mocha latte, please, and add a dash of peppermint to it.”

“That’s a change from your usual recipe, Susan.”

“Yes,” <side glance my way> “I’m splitting my timeline. Thanks, Al. Ok, Sy, let’s go for it.”

“It’s about degrees of freedom.”

“I like freedom, but I didn’t know it comes in degrees.”

“In certain contexts that’s a matter of geography, law and opinion. I’m talking Physics here. For physicists each degree of freedom in a system is a relevant variable that’s independent of other specifications. Location parameters are a prime example. On a Star Trek vessel, how does the Captain specify a heading?”

“When they know where they’re going she’ll say ‘Set coordinates for‘ wherever, but for a course change she’ll say ‘some‑number MARK some‑number‘. Ah, got it — that’s like latitude and longitude, two arcs along perpendicular circles. Two angles and a distance to the target make three degrees of freedom, right?”

“A‑k‑a three dimensions of space. How about time?”

“All you can do is go forward, no freedom.”

“Not quite. Conceptually at least, you can go forward and back. Timewise we’re moving along a line. That’s a one‑dimensional thing. Combine time and space as Minkowski recommended and you’ve got a four‑dimensional spacetime. Relativity may serve us time at different rates but we’re still trapped on that line.”

“Ah, now I see why you said five dimensions. High school geometry — you’d need a second time dimension to angle away from the one we’re on. Ooo, if it’s an angle we could do time‑trigonometry, like the sine would measure how different two timelines get divided by how long it took to get there.”

“Cute idea, Susan, but defining time fractures in terms of time would be a challenge. I think a better metric would be probability, like what are the odds that things would be this different?”

A rustle of satin behind me and a familiar voice like molten silver. “Hello, Sy, I read your posts about multiverses so I thought I’d drop by. You’re Susan? Hi, my name’s Anne.”

“Um … hello.” Anne is kind of breath‑taking.

“Hi, Anne. It’s been a while. Funny you should show up just as we’re getting to the idea of a probability dimension.”

“Mm-hm, how ’bout that? Sorry, Susan, but time‑trig won’t work. I’ve got a better idea for you. Sy’s physicists are so used to thinking thermodynamically. Entropy’s based on probability, isn’t it, Sy? The split‑off dimension should be marked off in units of information entropy.” <giggle> “You haven’t told Susan your twenty‑dimension idea yet, have you?”

“Anne, you’ve always been too fast for me. Susan, the Physics we have so far still has about twenty fundamental constants — numbers like the speed of light — whose values we can’t explain in our best models of how things work. Think of each as a coordinate in a twenty‑plus‑four-dimensional hyper‑Universe. The Anthropic Principle says we and my entire bubble Universe happen to be at the twenty‑way intersection where those coordinates are just right for life to exist. Each of your matryoshki Universes may or may not be there. “

“Lucky, aren’t we?”

~~ Rich Olcott

So Many Lunches

On By rolcottIn CosmologyLeave a comment

<shudder> “I don’t like Everett’s Many Worlds multiverse, Sy. When I think of all those A‑B entanglements throughout space I just see history as this enormous cable with an exponentially growing number of strands and it keeps getting thicker and more massive. Besides, that’s all about observations at the micro level and I don’t see how it can build up to make two me’s enjoying our different lunches.”

“Most physicists agree with you, Susan, although there have been entire conferences devoted to arguments for, against and about it. His proposal does solve several known problems associated with other interpretations of quantum mechanics but it raises some of its own. To my mind, it just tastes bad. How about another multiverse idea?”

“Is it as cumbersome as that one?”

“Well, it still involves infinity, but probably a smaller one. I think the best way to describe it is to start with black holes. Each one has a region at its geometric center where spacetime is under such stress that we don’t have the physics to understand what’s going on in there. You with me?”

“So far. I’ve read some of your posts about them.”

“Cool. Anyway, one conjecture that’s been floating around is that maybe, especially for the supermassive black holes, the energy stress is so high that Nature relieves it by generating a new blister of spacetime. The blister would be inside the Event Horizon so it’s completely isolated from our Universe. Visualize one of those balloon artists who twists a patch on the surface of a blown-up balloon and suddenly it grows a new bubble there.”

“Like yeast budding new yeastlets?”

“That’s the idea, except these spacetime buds would be rooted inside our Universe like a yeast cell’s internal vesicles rather than budding from the cell’s surface. Because it’s isolated, each bud acts as an independent Universe.”

“But Hubble has shown us a trillion galaxies. If there’s a supermassive black hole at the center of nearly every galaxy…”

“Yup, lots of Universes. But it gets better—”

“I see where you’re going. Each baby Universe can have its own collection of black holes so you can have a cascade of Universes inside Universes like a matryoshka doll. Except the people in each one think theirs is the size of a whole Universe. If there are people there.”

“All of that’s possibly true, assuming there are baby Universes and they have the same physical laws and constants that we do. The speed of light could be different or something. Anyway, I was going to a less exotic scheme. The Observable Universe is the space that contains all the light that’s been directed towards us since the Big Bang 13.7 billion years ago. Thanks to the expansion of the Universe, it’s now a sphere 93 billion lightyears in diameter. Think of it as a big bubble, okay?”

“Mm-hm. You’re thinking about what’s outside that bubble?”

“Mm-hm. Of course light and information from outside haven’t had time to get to us so we have no chance of observing what’s out there and vice‑versa. Do you agree it’s reasonable to assume it’s all just more of the same?”

“Sure.”

“Well then, it must also be reasonable to assume that our observability bubble is surrounded by other observability bubbles and they’re surrounded by more bubbles and so on. The question is, does that go on infinitely far or is there an outermost shell?”

“By definition there’s no way to know for sure.”

“True, but it makes a difference when we’re thinking about the multiverse. If there’s only a finite number of bubbles, even if it’s a big number, then there’s a vanishingly small chance that any of them duplicates ours. No copies of you trying to decide between noodles for lunch or a sandwich. If the number is infinite, though, some cosmologists insist that our bubble in general and you in particular must be duplicated not just once but an infinite number of times. Some of you go for noodles, some for sandwiches, some maybe opt for pizza. All in the same consistent Universe but disconnected from each other by distance and by light’s universal speed limit. Does that count as a multiverse?”

~~ Rich Olcott

Noodles or A Sandwich?

On By rolcottIn Cosmology, Physics: Quantum Mechanics, UncategorizedLeave a comment

“Wait, Sy, your anti-Universe idea says there are exactly two um, sub‑Universes. Even the word ‘multiverse‘ suggests more than that.”

“You’re right, Susan, most of the multiverse proposals go to the other extreme. Maybe the most extreme version grew in reaction to one popular interpretation of quantum theory. Do you know about the ‘Many Worlds‘ notion?”

“Many Worlds? Is that the one about when I decide between noodles for lunch or a sandwich, the Universe splits and there’s one of me enjoying each one?”

“That’s the popular idea. The physics idea is way smaller, far bigger and even harder to swallow. Physicists have been arguing about it for a half‑century.”

“Come again? Smaller AND bigger?”

“Smaller because it’s a quantum‑based idea about microscopic phenomena. Doesn’t say anything about things big enough to touch. Remember how quantum calculations predict statistics, not exact values? They can’t give you anything but averages and spreads. Einstein and Bohr had a couple of marquee debates about that back in the 1930s. Bohr maintained that our only path to understanding observations at the micro‑scale was to accept that events there are random and there’s no point discussing anything deeper than statistics. Einstein’s position was that the very fact that we’re successfully using an average‑based strategy says that there must be finer‑grained phenomena to average over. He called it ‘the underlying reality.’ The string theory folks have chased that possibility all the way down to the Planck‑length scale. They’ve found lots of lovely math but not much else. Hugh Everett had a different concept.”

“With that build‑up, it’d better have something to do with Many Worlds.”

“Oh, it does. Pieces of the idea have been lying around for centuries, but Everett pulled them all together and dressed them up in a quantum suit. Put simply, in his PhD thesis he showed how QM’s statistics can result from averaging over Universes. Well, one Universe per observation, but you experience a sequence of Universes and that’s what you average over.”

“How can you show something like that?”

“By going down the rabbit hole step by step and staying strictly within the formal QM framework. First step was to abstractify the operation of observing. He said it’s a matter of two separate systems, an observer A and a subject B. The A could be a person or electronics or whatever. What’s important is that A has the ability to assess and record B‘s states and how they change. Given all that, the next step is to say that both A and B are quantized, in the sense that each has a quantum state.”

“Wait, EACH has a quantum state? Even if A is a human or a massive NMR machine?”

“That’s one of the hard‑to‑swallows, but formally speaking he’s okay. If a micro‑system can have a quantum state then so can a macro‑system made up of micro‑systems. You just multiply the micro‑states together to get the macro‑state. Which gets us to the next step — when A interrogates B, the two become entangled. We then can only talk about the combined quantum state of the A+B system. Everett referred to an Einstein quote when he wrote that a mouse doesn’t change the Moon by looking at it, but the Moon changes the mouse. The next step’s a doozy so take a deep breath.”

“Ready, I suppose.”

“B could have been in any of its quantum states, suppose it’s #10. After the observation, A+B must be an entangled mixture of whatever A was, combined with each of B‘s possible final states. Suppose B might switch to #42. Now we can have A+B(#42), separate from a persisting A+B(#10), plus many other possibles. As time goes by, A+B(#42) moves along its worldline independent of whatever happens to A+B(#10).”

“If they’re independent than each is in its own Universe. That’s the Many Worlds thing.”

“Now consider just how many worlds. We’re talking every potential observing macro‑system of any size, entangled with all possible quantum states of every existing micro‑system anywhere in our Observable Universe. We’re a long way from your noodles or sandwich decision.”

“An infinity of infinities.”

“Each in its own massive world.”

“Hard to swallow.”

~~ Rich Olcott

The Futile Search for Anti-Me

On By rolcottIn CosmologyLeave a comment

“Nice call, Sy.”

“Beg pardon?”

“Your post a couple weeks ago. You titled it ‘Everything Everywhere All At Once.’ That’s the movie that just won seven Oscars — Best Movie, Best Director, Best Actress and Best Supporting Actress… How’d you predict it?”

“I didn’t, Susan. I wasn’t even trying to. I knew the movie’s plot was based on the multiverse notion. That’s the theme for this post series so it seemed like a natural cultural reference. Besides, that post was about the Big Bang’s growth in a skillionth of a second from a Planck‑length‑size volume out to our ginormous Universe and all its particles. ‘Everything Everywhere All At Once‘ seemed like a nice description of what we think happened. A mug of my usual, Al, and I’m buying Susan’s mocha latte.”

“Sure, Sy. Nice call, by the way. Have a couple of scones, you two, on me.”

“Thanks, Al, and thanks, Sy. You know, I’ve noticed the multiverse idea cropping up a lot lately. They used it in the Spiderman franchise, and the recent Doctor Strange pic, and I just read it’ll be in the next Flash movie.”

“Oh, it’s an old writer’s ploy, Susan. Been around in one form or another since Aristophanes invented Cloudcuckooland for one of his Greek comedies. Small‑screen scifi uses it a lot — Star Trek used it back in the Kirk-Spock shows and DS9 based a whole story arc on the idea. Any time an author wants to move the action to a strange place or bring in some variation on a familiar character, they trot out the multiverse. Completely bogus, of course — they may sound all science‑y but none of them have anything to do with what we physicists have been arguing about.”

“You mean your anti-Universe won’t have an evil version of you in it?”

“I certainly don’t expect it to if it even exists. Suppose an anti‑Universe is out there. Think of all the contingencies that had to go just right during 13½ billion anti‑years of anti‑quark‑soup and anti‑atomic history before there’s an anti‑planet just like Earth in just the right environment around an anti‑star just like ours, all evolved to the level of our anti‑when, not to mention the close shaves our biological and personal histories would have had to scrape through. I’d be amazed if even anti‑humans existed there, let alone individuals anything like you and me. Talk about very low probabilities.”

“You’ve got a point. My folks almost didn’t survive the war back in Korea. A mine went off while they were working in our field — another few feet over and I wouldn’t be here today. But wait, couldn’t everything in the anti‑Universe play out in anti‑time exactly like things have in ours? They both would have started right next to each other with mirror‑image forces at work. It’d be like a pool table show by a really good trick‑shot artist.”

“If everything were that exactly mirror‑imaged, the anti‑me and I would have the same background, attitudes and ethics. The mirror people on those scifi shows generally have motives and moral codes that oppose ours even though the mirror characters physically are dead ringers for their our‑side counterparts. Except the male evil twins generally wear beards and the female ones use darker eye make‑up. No, I don’t think mirror‑imaging can be that exact. The reason is quantum.”

“How did quantum get into this? Quantum’s about little stuff, atoms and molecules, not the Universe.”

“Remember when the Universe was packed into a Planck‑length‑size volume? That’s on the order of 10‑35 meter across, plenty small enough for random quantum effects to make a big difference. What’s important here, though, is everything that happened post‑Bang. The essence of quantum theory is that it’s not clockwork. With a few exceptions, we can only make statistical predictions about how events will go at microscopic scale. Things vary at random. Your chemical reactions are predictable but only because you’re working with huge numbers of molecules.”

“Even then sometimes I get a mess.”

“Well then. If you can’t reliably replicate reactions with gram‑level quantities, how can you expect an entire anti‑Universe to replicate its partner?”

“Then <singing> there can never be another you.”

~~ Rich Olcott

A Two-Way Stretch, Maybe

On By rolcottIn Cosmology, Uncategorized1 Comment

“Okay, Moire, I guess I gotta go with the Big Bang happening, but I still have a problem with it making everything come from a point full of nothing.”

“Back at you, Mr Feder. I have problems with your problem. To begin with, forget about your notion of a point with zero size. There’s some reason to think the Bang started with an event sized on the order of the Planck length, 10-35 meter. That’s small, but it’s not zero.”

“I suppose, but with the whole mass of the Universe crammed in there, ain’t that a recipe for the ultimate black hole? Nothing could get outta there.”

“Nothing needs to. What’s inside is already everything, remember? Besides, there isn’t an outside — space simply doesn’t exist outside of the spacetime the Bang created. Those bell‑shaped ‘Evolution of The Universe‘ diagrams are so misleading. I say that even though I’ve used the diagram myself. It’s just a graph with Time running along the central axis and Space expanding perpendicular to that. People have prettied it up to make it cylindrical and added galaxies and such. The lines just represent how much Space has expanded since the Bang. Unfortunately, people look at the bell as a some kind of boundary with empty space outside, but that’s so wrong.”

“No outside? Hard to wrap your head around.”

“Understandable. Only physicists and mathematicians get used to thinking in those terms and mostly we do it with equations instead of trying to visualize. Our equations tell us the Universe expands at the speed of light plus a bit.”

“Wait, I thought nothing could go faster than the speed of light.”

“True, nothing can traverse space faster than light or gravity, but space itself expands. At large distances it’s doing that faster than light. We actually had to devise two different definitions of distance. ‘Co‑moving distance‘ includes the expansion. ‘Proper distance‘ doesn’t. In another couple billion years, the farthest things we can see today will be co‑moving away so fast that the photons they emit will be carried away faster than they can fly towards us. Those objects will leave our Observable Universe, the spherical bubble that encloses the objects whose light gets a chance to reach us.”

“My head hurts from the expanding. Get back to the Bang thing ’cause it was small. Too small to hold atoms I guess so how can it explode to be everything?”

“‘Expand’, not ‘explode‘ — they’re different — but good guess. The Bang’s singularity was smaller than an atom by at least a factor of 1024, but conditions were far too hot in there for atoms to exist, or nuclei, or even protons and neutrons. Informally we call it a quark soup, which is okay because we think quarks are structureless points that can cram to near‑infinite density. We don’t yet know enough Physics for good calculations of temperature, density or much of anything else.”

“That’s a lot of energy, even if it’s not particles. Which is what I’m getting at. I keep hearing you can’t create energy, just transform it, right? So where did the energy come from?”

“That’s a deep question, Mr Feder, and we don’t have an answer or hypothesis or even a firm guess. It gets down to what energy even is — we’re just barely nibbling at the edges of that one. One crazy idea I kind of like is that creating our Universe took zero energy because the process was exactly compensated for by creating an anti‑Universe whose total anti‑energy matches our total energy.”

“Whaddaya mean, anti‑Universe and anti‑energy?”

<deep breath> “You know an atom has negatively‑charged electrons bound to its positively‑charged nucleus, right? Well, the anti‑Universe I’m thinking of has that situation and everything else reversed. Positive electrons, negative nucleus, but also flipped left‑right parities for some electroweak particle interactions. Oh, and time runs backwards which is how anti‑energy becomes a thing. Our Universe and my crazy anti‑Universe emerge at Time Zero from the singularity. Then they expand in opposite directions along the Time axis. Maybe the quarks and their anti‑quarks got sorted out at the flash‑point, I dunno.”

“So there’s an anti‑me out there somewhere?”

“I wouldn’t go that far.”

~~ Rich Olcott